Looks like the asphalt slopes toward it which would direct stormwater into it. There's also no gutters on the building in the back, so that water would just hit the pavement and run off. There's also a pump-looking gizmo in the lower-right corner that appears to have a discharge hose going away from the structures on the property.
Or for propane tanks. They need to have an area underneath to catch the gas if they star leaking. And the bumps can be some kind of foundation for putting the tanks. It looks like it could hold two tanks next to each other.
If you have something that looks like a pool they’ll go swimming.
The ladder gets them out and the humps give them a place to stand in the middle to keep their heads above the water line. Their arms get tired very quickly.
The element that makes me think no one has gotten it right are the stairs. People enter and exit this when it is full.
I am willing to wager internet points that this is for washing or fluid based differentiation of materials. The dividers structure would be some form of flow distribution control or cleanup system.
Possibly a slurry pond? The only pools like that I've seen on farms were all on dairies; and they dump the cow piss and shit in them. I've also seen above ground cess pools like this at some industrial factories in the boonies. Used to be a tarmic plant outside my hometown that used one.
Could be a hog house sewage slurry lagoon, I see what looks like a pump out on the far right corner. I'm not sure about the humps on the bottom, but they might control the current to avoid a whirlpool effect when pumping out the pond. Just guessing here.
Maintenance on most large farm equipment is performed from the side. In a pinch, the undercarriage is also usually several feet off the ground at rest because it needs significantly more ground clearance than a road vehicle.
Definitely not rice. That’s farmed on huge fields and have (in USA at least) telltale levy lines which are used to control flooding the fields. Poke around in northeast Arkansas and you should find some.